Different residues in the SARS-CoV spike protein determine cleavage and activation by the host cell protease TMPRSS2
Fig 3
Mutations K543A/R544A and R563A/K566A interfere with SARS S trafficking through the constitutive secretory pathway.
(A) COS-7 cells were cotransfected with expression plasmids for SARS S wt or the indicated mutants and with a plasmid encoding YFP fused to a plasma membrane anchor (red color). After staining for SARS S with V5 antibody and anti-mouse Alexa Fluor 647 secondary antibody (green color) the cells were analyzed by confocal microscopy. Similar results were obtained in a second independent experiment. (B) The experiment was carried out as described for panel A, but GFP fused to a Golgi marker (red color) was used instead of YFP with plasma membrane anchor. The results were confirmed in a second separate experiment. For optimal visualization, colors were manually assigned with LSM Pascal 5 software version 3 and do not correspond to the actual emission spectra of YFP, GFP and Alexa Fluor 647.